Investigations are directed at host defense mechanisms and immuno-regulation in malaria and leishmaniasis, and the possible role of the schistosomal egg granuloma in regulation of hepatic fibrosis. Presently, research is aimed at (1) spleen function in malaria immunity (2) regulation of intracellular growth of leishmania in human macrophages, and (3) characterization of a fibroblast stimulating factor produced in vitro by schistosomal egg granulomas. In addition, clinical studies are covered by project Z01 AI 00141-02 FY 1978.